This invention relates to a connector comprising a plurality of contact arrays and, in particular, to a connector suitable for high-speed differential signal transmission.
At first, high-speed differential signal transmission will be described. The high-speed differential signal transmission has two types of transmission modes, i.e., an unbalanced (single-end) type and a balanced (differential) type. The single-end type is a mode in which a high level and a low level of a digital signal are distinguished by the potential difference between a ground line and a signal line, and is generally used so far. On the other hand, the differential type is a mode in which two signal lines (+, −) are used and the high level and the low level are distinguished by the potential difference between the two signal lines. In the differential type, two signals on the two signal lines are equal in voltage level to each other and different in phase by 180° from each other. As compared with the single-end type, the differential type assures reliable transmission because noise produced in the two signal lines is canceled at the receiver input.
Besides, there is another transmission mode according to TMDS (Transition Minimized Differential Signaling). The TMDS is a standard for exchange of image data between a PC main body and a display monitor, and is a mode in which data transmission is performed by the use of two signal lines (+, −) and a single ground line.
In an existing connector comprising signal contacts and ground contacts, use is made of a structure in which the signal contacts and the ground contacts are faced to each other in a grid-like pattern or a structure in which the ground contacts are partially skipped. In the former structure, the number of contacts is increased so that miniaturization of the connector is difficult. In the latter structure, the high-frequency characteristics of the connector are considerably degraded.
At present, transmission of high-speed differential signals is required in a growing number of software applications. Under the circumstances, there is a demand for a connector having a compact size, a low price, and excellent high-frequency characteristics.